Not easy to provide a simple answer, and not sure your question is about the M&A process or the PMI one.
But if (so many ifs):
– the size of the acquired company is small (less than 1000 employees?)
– it has only one main facility in a country where the acquiring company is already present (meaning a single country known regulation)
– the business is similar or comparable between the 2 companies
– the scope of the integration covers activities from the main value chain and support functions
– you have a decent dedicated integration team and integration capabilities like data migration, infrastructure, collaboration tools…
– probably others…
The minimum timeline I can think of is between 12 and 18 months as you need to give enough space for the communication and change to happen – not only for employees, but as well for leadership, customers, vendors, authorities and other external partners…